L 4.1.4 Quiz: Using the Mole Question 9 of 10
Which of the following best describes an empirical formula?
A. A chemical formula that uses the numbers of atoms of each
element as they actually occur in a molecule
B. A chemical formula that shows the relative number of each type of
atom in a molecule, using the smallest possible ratio
C. A chemical formula that lists the percent composition of each
element
D. A chemical formula that identifies the oxidation state of each
element

B. A chemical formula that shows the relative number of each type of

atom in a molecule, using the smallest possible ratio

Explanation:

The empirical formula of a compound shows the relative number of each type of atom in a molecule and it uses the smallest possible ratio.

a. energy is absorbed in the reaction.

if in a given reaction the energy of products is greater than the energy of reactants it means that reaction is endothermic and during the reaction, the energy is absorbed by reactants. in an endothermic reaction, the products have more stored chemical energy than the reactants. and in this reaction the reactants are more stable than products before the compounds with less energy are always more stable.

as given the equation is

2al + 6 hcl > 2 alcl3 + 3 h2(g)

as per equation two moles of aluminum reacts with six moles of hcl to give two moles of alcl3 and three moles of hydrogen gas

given: three moles of al are present and 7 moles of hcl

for three moles of aluminum nine moles of hcl will be required

however as 7 moles of hcl are present so the limiting reagent is hcl

hcl is going to decide the number of moles of product formed

when six moles of hcl are present = 3 moles of h2 are formed

when one mole of hcl is present == 3/6 mole sof h2 will be formed

when 7 moles of hcl are present = 3 x 7/ 6 moles of h2 will be formed = 3.5 moles of h2